The present invention relates to a type face striking system for a typewriter or similar machine of the type which includes an electromagnetically actuated printing hammer.
In such electromagnetic striking system, the printing hammer is accelerated, by means of a short voltage pulse applied to a winding, from its rest position to its striking position. Upon reaching the striking position, the hammer drives a type face to make an imprint on a record carrier via an inked ribbon. The type face to be struck is here disposed, for example, directly on the printing hammer or on a type carrier, for example a daisy wheel, which must be properly positioned before the imprint is made.
The return of the printing hammer into its rest position is then effected by the kinetic energy from impact on the printing abutment and is aided by the force of a spring if a faster return is necessary for faster reusability of the printing hammer. However, the presence of such a spring is a drawback during the striking movement, because the resetting force of this spring must then additionally be overcome.
So-called electrodynamic striking systems, such as disclosed, for example, in DE-OS [German Laid-open Application] 3,038,881, laid open on May 19th, 1982, avoid this drawback. Here, permanent magnets generate a magnetic field and the printing hammer is mounted so as to be movable in the striking direction within this field. Additionally, a winding is provided to which is applied the voltage pulse which actuates the striking movement. The magnetic field generated by the winding, and acting in the opposite direction to the field produced by the permanent magnets, produces an acceleration of the printing hammer to the striking position, and the return movement of the printing hammer into the rest position, when the voltage pulse in the winding is terminated, is aided by the magnetic field of the permanent magnets.